I'm interested in making a small organ but I'd really like to avoid spending a lot. I'm already figuring out how to make the flue pipes from PVC but I can't seem to find a way to control 3 or 4 dozen valves without spending a lot. If possible I'd like to stay under $100 for at least just the solenoids or whatever I end up using. I figure they can be pretty small, even if they aren't strong enough I only need a very tiny amount of movement so I can find some way to give them more leverage.

Is there anywhere to get solenoids very inexpensively, or any other way of controlling valves inexpensively? At this point I'm willing to adapt the design to whatever type of part I end up using.

I can't find anything cheap enough on eBay (<$2) I was thinking about maybe having cork stoppers pushed against the pipes with springs and at the bottom of that little thing a permanent magnet, then just having a winding of wire to pull it down.

About how much wire does it take to get a reasonable amount of pull? (A few ounces worth maybe)

Ok, so I'm trying out my own solenoid. I using a plastic bobbin and 30 gauge magnet wire. I don't really know exactly how much but I think it's 100 to 150 feet. At 12v it seems to be powerful enough to attract or repel a magnet about the same diameter to or away about 1/2 inch but it gets pretty hot awfully fast. Just being on for a moment it's fine but after 10-20 seconds it gets almost too hot to touch and I'm afraid much after that it could melt the bobbin. It would never be on that long but it might be off and on repeatedly a lot for a while. So I'm wondering what I might be able to do about heat.

One idea was to use metal bobbins. The permanent magnets would be normally attracted so I could use the electromagnet to repel them. Then since they are metal I could attach them to a metal frame to sink the heat.

Is there another way to reduce the heat produced?

Also, I'm not sure if I should use a large diameter magnet on the top or bottom or if I should use a small magnet that can pass through the hole. Seems like a smaller magnet would be less attracted/repelled but also closer to the field. I'm not sure if that would be better or worse.

Then see how much less power will work (PWM, more to start the valve and less to keep it in place), maybe wrap the solenoid around thicker -soft iron- tube (heat sink mass) and pump air over/around/through the solenoid? Working the solenoids through levers can give you mechanical advantages that direct control will not. Hot solenoid is like a finger pressed hard.

Cost is a huge issue, if I could find a way to use these bobbins that would really be good. I'm going to try to experiment to see what kind of heat is generated from a typical amount of use of a commonly used key. Also, depending on how the mechanics work out I can likely lower the voltage if I can get the power I need.

But before I know that I need to know what the most efficient setup is for the permanent magnet. I assume a magnet going through the center is best. But should I spend more to get longer magnets? Or would that not help? Maybe it would help to some extent? I have no idea, does anyone know about that?

Have you googled them yet? Lots of hits for "homemade solenoid". Videos and images galore. Even step-by-step how to's.

This one is my favorite. It's about robotic xylophone, but the style might be useful for you. I thought solenoids usually use a steel slug, but these guys put a neodynium magnet on one end to make it stronger. It's a different sort of solenoid, though. They want it to be fast and do a hit, as opposed to staying on while a note is played.

I think they get around the heat issue by using more wire so it's a greater resistance.

Yeah, I've seen that one. I definitely need to use a magnet in place of a slug, mine has almost no pull to metal but plenty to a magnet. Unfortunately there's not a lot of info on the ideal magnet size or position so I might just have to experiment.

I am interested in this as I have a project in mind that could use 30 or so small solenoids.

Have you tried reducing the current through the coil to the point where it doesn't get hot, and at that point is there enough magnetic force to be useful?

If you think of a bobbin as short and fat have you tried winding a long thin solenoid with the same number of turns - it might allow the heat to escape more easily but I'm not sure what it would do to the magnetic force. You might need to use a long iron "magnet" slug. I think that a long thin solenoid might also keep the magnetic field closer to the slug - i.e the wire is nearer the centre.

Am I right in thinking that your valves will impose very little load on the solenoid?

...R

Two or three hours spent thinking and reading documentation solves most programming problems.